Essays on commodity cycles based on expanded Cobweb experiments of electricity markets

This thesis studies cycles in commodity markets. Such fluctuations have significant adverse effects onconsumers and producers. The properties of commodity price fluctuations are well known. However,there is considerable disagreement about the underlying causes of market fluctuations. Understandingsuch cycles is essential for policy analysis. We analyze the case of recently deregulated electricitymarkets, where several authors have expressed a concern that capacity cycles may emerge. Thepotential occurrence of cycles represents a major threat to electricity security, since there could beperiods with insufficient capacity to satisfy demand followed by periods with excess capacity andunsustainably low prices.Traditional economic literature argues that oscillations are caused by external shocks. We explore analternative explanation that comes from the internal structure of the system. The method is laboratoryexperiments. To link to the existing literature we start by investigating the simplest economic model ofcycles (the Cobweb model) with standard conditions, linear demand, and constant costs. Step by step,we add complexity (and realism) to the simple model. We introduce long lifetimes of productioncapacity and then we introduce a two period investment lag in addition to long lifetimes. Consistentwith previous experiments and the rational expectations hypothesis, we find no evidence of cycles inthe basic design and in the capacity lifetime treatment. Average prices are close to Cournot Nashequilibrium with a bias towards competitive prices. In the investment lag treatment, however, varianceand autocorrelation analysis indicate cyclical tendencies.In a follow up experiment we introduce a constant price elasticity with dynamic demand adjustment.The experiment gives rise to larger and asymmetric fluctuations similar to observed commodity prices(e.g. sugar and coffee prices). In a third experiment, we increase the frequency of decisions. Weobserve oscillatory behaviour in investment activity and prices. The cyclical tendency is stronger thanin the previous experiments, and the results corroborate assumptions made in previous simulationstudies of electricity markets. In a fourth paper, we look at empirical evidence of fluctuations in someelectricity markets in South America. While the time-series are not long enough to conclude that thereare systematic fluctuations, we observe that both Brazil and Chile have experienced very small reservemargins, electricity supply crises, and considerable shortages of electricity. The likely cause is lack ofinvestments in new generation capacity. Argentina and Colombia have high reserve margins and verylow spot prices, largely because of the deep recessions in their respective economies.The thesis contributes to a better understanding of endogenous causes of market fluctuations. Thisshould call for an increased interest in market models that include supply and demand side dynamics.Also, the findings should serve as a motivation to search for alternative stabilising policies in existingmarkets, particularly in markets where deregulation is considered

Integrated Modelling of Gas and Electricity Distribution Networks with a High Penetration of Embedded Generation

Gas-based combined heat and power (CHP) has matured enough to be regarded as the next evolutionary step in promoting energy efficiency use in the urban environment. Although its potential market is increasing, little research has been conducted into the combined technical effects that a high penetration of these units may have on both natural gas and electric (G&E) distribution networks. This paper presents a power flow tool that performs a simultaneous assessment on some technical impacts that a high penetration of heat-driven cogeneration units may have on G&E networks. A case study is presented and results show that as expected, the gas demand increases as well as the losses associated with its delivery, while the opposite effects occur in the electrical system. However, less evident is the load profile variations distribution networks will experience and that overall energy losses will vary according to the CHP penetration and the type of technology used. The study shows that an integrated G&E analysis offers a fresh perspective in quantifying the effects cogeneration technologies will have on energy distribution networks

Fuel consumption minimization of a microgrid

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El padre Flórez y la Biblioteca Histórica de la Universidad Complutense

La relación del padre Enrique Flórez (OSA) con la Universidad Complutense, es ampliamente conocida; sin embargo, no se ha estudiado hasta ahora la relación concreta del Padre Flórez con la Biblioteca de esta Universidad que queda patente en algunos hechos como el intento de impresión del Códice Complutense o Biblia visigótica de Alcalá, o su papel como bibliotecario del Real Colegio de San Agustín de la Universidad de Alcalá. Se incluye, además, una relación de las obras del Padre Flórez de las que existen ejemplares en la Biblioteca Histórica de la Universidad Complutens

Theory of Auger core-valence-valence processes in simple metals. II. Dynamical and surface effects on Auger line shapes

ABSTRACT: Auger CVV spectra of simple metals are generally believed to be well described by one-electronlike theories in the bulk which account for matrix elements and, in some cases, also static core-hole screening effects. We present here detailed calculations on Li, Be, Na, Mg, and Al using selfconsistent bulk wave functions and proper matrix elements. The resulting spectra differ markedly from experiment and peak at too low energies. To explain this discrepancy we investigate effects of the surface and dynamical effects of the sudden disappearance of the core hole in the final state. To study core-hole effects we solve Mahan —Nozieres —De Dominicis (MND) model numerically over the entire band. The core-hole potential and other parameters in the MND model are determined by self-consistent calculations of the core-hole impurity. The results are compared with simpler approximations based on the final-state rule due to von Barth and Grossmann. To study surface and mean-free-path effects we perform slab calculations for Al but use a simpler infinite-barrier model in the remaining cases. The model reproduces the slab spectra for Al with very good accuracy. .In all cases investigated either the effects of the surface or the effects of the core hole give important modifications and a much improved agreement with experiment

Assessment of power losses of an inverter-driven induction machine with its experimental validation

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